Things could get interesting.

The race to succeed Jeremy Corbyn looks set to start in earnest after Labour’s ruling body backed the creation of a brand new post of female deputy leader.

The National Executive Committee (NEC) voted on Saturday to formally support a radical rule change to establish a second deputy to serve alongside Tom Watson.

With many in the party demanding that its next leader should be a woman, the election of the new position is sure to be seen as a proxy for the battle to replace Corbyn whenever he steps aside.

The move came as the NEC also decided against plans to introduce mandatory reselection of sitting Labour MPs, opting instead to reduce the threshold of party members and unions needed to force a challenge.

Just a third of local members will be needed to trigger a selection contest, a move that could oust several current MPs who have clashed with their local parties.

Trade unions also won a key say in future leadership elections, with the NEC backing a new system whereby a candidate would get on the ballot if they had 10% of MPs or 5% or local parties or unions. Allies of Corbyn had wanted just 5% of MPs’ nominations to be required.

The series of votes by the NEC was seen as a victory by trade unions and centrists, not least as the leadership opposed the creation of the new female deputy post, one source told HuffPost UK.

Among the contenders for the new role touted by senior figures in the party are Shadow Education Secretary Angela Rayner, Shadow Foreign Secretary Emily Thornberry, Shadow Business Secretary Rebecca Long-Bailey and Shadow Equalities Minister Dawn Butler.

Shadow Home Secretary Diane Abbott, who has run for leader before, could be another popular contender among members.

Labour has long been taunted by the Conservatives, who have had two female PMs in Margaret Thatcher and Theresa May, for their failure to elect a female leader.

The NEC backed the female second deputy post after trade unions and Watson himself swung behind the idea at its meeting on the eve of the Labour conference in Liverpool.

The idea was originally seen as a way of sidelining Watson, who in 2016 was highly critical of Corbyn, and diluting his own power. But he led calls in the NEC meeting to support the new post.

Late last week, Watson told the BBC he was ‘strongly in favour’ of the idea. “I think it’s really important that we continue the battle for gender parity in our party, that’s Jeremy’s aim as well,” he said.

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Jeremy Corbyn and Dawn Butler

The rule change was proposed by the Wirral West constituency party and will now be voted on on Tuesday.

If it is passed by conference, the NEC will then go away and draft details on next steps including the timing and procedure for a second deputy election.

HuffPost understands that a review will also take place of the role that ‘registered supporters’ will be able to play in future leader and deputy leadership elections.

Some believe that registered supporters could be used to add a huge boost to any deputy candidate who comes out firmly in favour of a ‘People’s Vote’ on Brexit.

Elsewhere, the NEC meeting marks a setback for the grassroots group Momentum, which had argued for ‘open selections’. Founder Jon Lansman pushed for the idea and opposed the 10% MP threshold for leadership nominations.

A Labour Party source said: “The proposal agreed unanimously by the NEC reforms the existing re-selection process, giving members and trade union affiliates a greater say in who represents them, but doesn’t move to automatic open selections.”

The NEC agreed a statement on the Democracy Review, which will be published on Sunday morning in the Conference Arrangements Committee report, along with a series of rule changes which delegates will vote on.

On reselections, the NEC agreed unanimously to propose a rule change to reform the trigger ballot process.

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Labour MP Joan Ryan recently lost a vote on confidence by her local party

Under current rules, every Labour MP has to undergo a trigger ballot process in the run-up to a General Election, but they automatically avoid a contest unless more than 50% of local branches want one.

The rule change agreed by the NEC on Saturday reduces the threshold to 33%, triggered by either the 33% of party branches or 33% of affiliated trade union branches. The proposal, along with other NEC rule changes, will be put to the vote on Sunday.

Several Labour MPs have recently lost votes of confidence by their local parties, including Joan Ryan, Gavin Shuker, Frank Field and Kate Hoey.

One party source said: “The new two thirds rule could mean dozens of MPs are toast – on the hard left as well as ‘right’.”

Particularly vulnerable may be MPs on the Left who were imposed against the wishes of their members in emergency selections before the 2017 snap election.

On the leadership threshold, the NEC agreed unanimously to propose a rule change that would require candidates to obtain nominations from 10% of the PLP, plus nominations from 5% of Constituency Labour Parties (CLPs) or 5% of members of trade unions or affiliate organisations.

The current leadership nomination threshold is 10% of the PLP and does not include party members or unions. The rule change does not propose lowering this threshold, but proposes to give CLPs and trade unions a say in the balloting process.

Momentum had put huge pressure on NEC members to back open selections, but said it was pleased at some progress to make it easier for local people to have a say.

A Momentum source said: “The result of tonight’s NEC shows the power of grassroots campaigning.

“Thousands of members lobbied their NEC representatives, Momentum petitions gathered 50,000 signatures and while the members haven’t got everything they wanted, these proposals are a significant improvement on what was being discussed earlier in the week.

“The changes in selections rules will give members far more say in who represents them and result in more open selections.

“And while the slight increase in the threshold is deeply disappointing, we managed to avert disaster and avoid a dramatic increase to the leadership threshold which would have stopped a socialist candidate getting on the ballot in a future leadership contest.

“Long term Momentum will continue to campaign for full open selections and to abolish the MP veto over leadership candidates.”